1. Field of Invention
The invention relates to an apparatus and a method for de-interlacing a frame and, in particular, to an apparatus and a method for adaptive de-interlace of a frame.
2. Related Art
According to the well-developed technology, the displaying quality of video media is greatly progressed. However, different image processing methods may affect the displaying quality while displaying the video media. The different processing methods are, for example, the interlace scan method and the progressive scan method.
An interlace scan frame is composed of two fields, wherein each field includes only the odd scan lines of the frame or the even scan lines of the frame. In the interlace scan frame, the resolution of each odd field and/or even field is only half of the original frame. The advantage of the interlace scan method is to smoothly display the dynamic image, and the disadvantage thereof is to cause the blurring in the displayed image. The scan speed of the progressive scan is twice of the interlace scan, so that the progressive scan can present fine and clear frames. As a result, the present advanced video apparatus adopts the progressive scan method for scanning and displaying.
Regarding to the scan standard of present analog televisions, the most popular standards includes the Television Standards Committee (NTSC) system and Phase Alternation by Line (PAL) system. The NTSC system adopts the interlace scan method, so that if the image of the NTSC system is displayed in a progressive scan display system, the displayed frame only includes the odd field or the even field resulting in the poor image resolution (only half of the original image resolution). Therefore, the display quality of the image is unsatisfied. In addition, if an interlace scan DVD image is directly displayed on a progressive scan display system, the above-mentioned problem also occurs. To solve the above-mentioned problem, the interlace scan image must be de-interlaced. In other words, the de-interlace process is a way for transforming the interlace scan image into the progressive scan image.
The de-interlace processes include two typical linear transform technologies, which are weave and bob de-interlace processes. Referring to FIG. 1A, the weave de-interlace process is to overlaid or weave two input fields (including an odd field and an even field) for generating a progressive frame. As shown in FIG. 1B, the bob de-interlace process is to accept only one input field, such as the even frame only, and to discard the other field, such as the odd frame. Thus, the resolution of the vertical direction of the frame is decreased to half of the original image. To recover the resolution of the image, two adjacent scan lines of the same field are used to compensate the scan line there between in the discarded field.
The weave de-interlace process has better effects for static images, but may have misalignment for the dynamic images, which results in the serrations at the edge of the frame and decreases the displaying qualities. The bob de-interlace process may overcome the misalignment problem to obtain clear and nature dynamic images. However, for the static images, the bob de-interlace process decreases the vertical resolution of the images and then compensates it by the interpolation method. Thus, the displayed frame becomes blurred and is not sharp.
It is therefore a subjective of the invention to provide an apparatus and a method for adaptive de-interlace of a frame, which can select the proper de-interlace algorithm according to the interlace scan frame to be processed, so as to employ the suitable de-interlace method to process the dynamic or static image. Thus, the displaying qualities can be enhanced.